The Doctor and the Avatar
by Erroltheowl
Summary: The Gaang are in a spot of trouble when a strange man appears to lend a hand. The last Airbender and the last Time Lord work together to save the world.


Avatar: The Last Airbender- Dr Who Crossover

The Tardis landed with a thud. The Doctor lurched forward a little, slamming a lever down and twiddling a dial on the consol as he did so. As the wheezing and whirring sound of the Tardis faded the Doctor ran and jumped from the grille platform, grabbing his coat and straightened his tie; London in the 1920s - he certainly wasn't going to look shabby.

The Doctor reached for the door with the familiar pang of excitement and almost turned to grin at Donna or Martha or Rose or any of them, half expecting a laugh, a look of tentative excitement with the joy and wonder of time travel in their eyes...

The smile slipped off his face and the emptiness of the Tardis stared back at him. There was a time when remembering felt like a punch to his hearts. Now it felt like a dull ache, the kind that settles on your shoulders, lingering and whispering to you. God, he felt old.

The Doctor grimaced and shook his head. He was here to enjoy himself and he was determined to do just that. He ran a hand through his hair, adjusted the lapels of his jacket and marched out the door.

xxx

Aang leapt from the roof, somersaulted and launched an air-strike at the creature. He missed by a hair's breadth and landed briefly on the ground only to kick back into the air once more. The creature was clawing its way up the same roof Aang himself had just vacated; brocken tiles skittered to the ground and smashed.

Aang landed on the roof above the creature, which opened its jaws wide revealing huge, sharp teeth.

"I don't want to hurt you!" Aang yelled, balancing on the central beam of the roof. But the animal gave a scream of anger and began to pull itself up the roof with incredible speed. But it was not quick enough: Aang jumped clean over the monster and with a swift twist of his body, sent another blast of air, quickly followed by to two short jabs of fire. Hoping to disorientat the thing rather than hurt it, Aang tried to force it back to the ground and away from the village.

But the thing did not seem to mind the fire. If anything he had only managed to anger it further. It swiped at Aang with long metalic-looking claws.

Gritting his teeth he used airbending to propel himself to the main square and by the sounds of it the creature was following. Aang landed lightly, widenening his stance and with one graceful movement he pulled the water from the village well behind him and doused it over the oncoming creature.

Aang had fully expected the thing to keep on coming or maybe (if he was lucky) back off. But instead it stopped dead in its tracks and began to shudder. Aang heard a fizz and a crackling and as he looked blue sparks began to emit from the creature's wide yellow eyes and gaping mouth. It shook its head, like a dog ridding itself of an irksome fly but still the crackling, grinding, scraping noises continued. Aang stared, confused. What was this thing? He had never seen anything like it before. Maybe it was for the spirit world?

Whatever it was, it certainly didn't like water. With a final howl it turned and began to run. There was a shimmer, almost like a mirage; Aang blinked and the thing was gone.

xxx

"Quick, get behind me!" the Doctor shouted and the few villagers still out obeyed without question. The Doctor flicked his Sonic Screwdriver and advanced on the beast before him. "All right there little fella..." he said, though of course there was nothing little about it but at least it was furry. "What are doing here, eh? Who sent you?"

"Don't try to reason with it!" cried a man from behind him.

The Doctor ignored the villager and took another step closer. The beast snarled, its hackles raised. It looked ready to pounce.

Just perfect. So much for London. So much for the raging '20s. He had been here barely five minutes when the screaming had started. Why was there always screaming? People needing saving? Was it too much to ask for a quiet life? The Doctor smiled to himself. Where would be the fun in a quiet life?

He took another step forward and pushed a small button on the Sonic. The blue light lit up and the high pitched whirring emanated as he scanned the creature.

"Well...You're not from around here are you, Fido?" he said, holding the screwdriver up to his eyes. "You're a long way from home."

He looked back at the dog-like beast but it had sopped dead. It sat down. There was flicker in the air and it vanished.

"Damn." The Doctor shook his head in frustration, "In built tellaportation. I hate it when they do that!"

"You saved us!" cried the man, who came out from his hiding place behind some dustbins and shoo the Doctors hand vigourously.

"Thank you! Thank you!" cried another woman, hugging him around the middle. "We're saved!" she shouted over to her family, who were hanging out a window, "This strangely dressed man has saved us!"  
"Oh...Well," said The Doctor grinning in an abashed sort of way. "Glad to help."

The words had barely left his lips when there was a crash and roar from the other end of the street.

"There are more of them!" sobbed the woman. "Will you help us kind stranger?"

"Get inside and lock your doors," said the Doctor. He was about to run towards the sound of the growling when something shot up into the sky. The Doctor squinted up and could make out a blur of orange. Anther howl pierced the air and then he saw it, there on a roof top. The orange blur sped towards the monster and, from a good few metres away, sent it sprawling back down onto the street.

"What the..."

"It's the Avatar!" yelled a voice in delight

"The Avatar? Wait, hang on!" The Doctor slapped himself on the forehead. "I know where I am!"

"That's good to know sonny. Now how's about helping us from these spirit monsters." The Doctor stared at the little old man who had spoken. _Sonny?_

The Doctor ran to the end of the street. There was no sign of the orange blur or the creature but a crowd was gathering in the main square, grouped around a small podium, where a young girl was standing. He edged close enough to hear what she was saying.

"Listen up, people," she called, authority in her voice. "We don't know yet what these things are but we now know that they can be fought with water. It's like they're allergic to it. So if you see one arm yourselves with water. Don't get too close to them though." she added carefully, "Now the Avatar is going to be in the area until we find out where these things came from and how to send them back. But for now, just stay alert and don't wander off anywhere alone."

The girl hopped down from the podium as the crowd began muttering nervously. The Doctor stood on tiptoe, for the girl was suddenly lost in the group of onlookers. He spotted her walking away with another, taller boy dressed in a similar blue tunic to the one she wore.

"Excuse me," he said to a passing boy, "Been out of town for a while. Bit behind the times...Who was that?"

The boy blinked, "That's Katara."

"Right...and who would she be?"

The boy giggled, "She's with the Avatar," he said, as though that explained it.

"Uh huh...Do you know where I could find the Avatar?"

"mmhh, folks are saying he's staying up at the old temple." the boy waved at the mountains behind him. "But it takes days to climb up there. Unless you have a flying bison." The boy seemed to find this extremely funny. He gave the Doctor an amused stare and then skipped off to find his parents.

The Doctor looked over the mountains, shielding his eyes from the sun. He didn't have a flying bison but he thought he could do one better.

xxx

"Thank you Avatar Aang! Our village owes you greatly."

"Not a problem sir," said Aang, smiling at the old man. He always appreciated the thanks he got but he couldn't pretend that he wasn't tired. The thought of their camp back at the Air Temple and of dinner cooking on the fire made it hard not to fly back there straight away. But he had to make sure everyone was safe and that no more of the spirit beats turned up.

"I just wondered Avatar," said the old man, "Was he with you? The strange one?"

"Who?"

"Strange young man... helped fight off the beasts."

"You mean Sokka?"

"Hey!" came Sokka's affronted voice from behind him. "I'm not strange!"

"No, it wasn't him," said the man with a small bow to Sokka who sniffed, looking appeased. "No, it was a strange man in strange clothes with strange hair...he had a stick thing that glowed blue...He made the creature disappear."

Aang frowned. "Did he give a name?"

The man shook his head. "I just assumed he was with you. Saved me and the family though, so you thank him if you see him."

"I will," said Aang but he frowned at Sokka, "Who do you think that could be?"

Sokka shrugged, clearly unconcerned. "Helpful stranger I guess. So what do we do now?"

Katara and Toph had joined up with him and were watching him expectantly. He chewed his lip for a moment, staring at the sun which was starting to sink in the sky. "I think you should fly to the surrounding villages, tell them what we know about the water."

"What about you?" said Katara.

"I'll stay here and try to help with some of the damage," he gestured to the general chaos that the beasts had left in their wake. "Plus I want to have a look for this stranger with the blue light thing."

"Why, what's so special about him?" said Toph.

"I dunno," replied Aang, rubbing his head, "But he took out one of those things without water. Maybe he knows something about them."

"Ok, well we'll see you in a few hours," said Sokka. With a hug from Katara and a punch on the shoulder from Toph, they departed.

Aang set about trying to help the villagers, using his earth and air-bending to lift the heavy rubble and beams that had fallen and to help fix the roads and stone structures. He asked around about the man but few had actually seen him. One woman said she had seen a tall man with spiky hair and odd-looking clothes and a small boy said that the man had asked about where he could find the Avatar.

When there was no more he could do, Aang bade farewell to the villagers, snapped open his glider and kicked off hard from the ground. The air cool and fresh on his face, he headed for the mountains.

xxx

The Doctor left his coat in the Tardis this time. It was far too hot outside – definitely not London.

He rolled up his shirt sleeves and loosened his tie and left the Tardis once more to a beautiful sight. The sun was setting, spilling colours across the sky and the mountain peaks. He stood in a crumbling sort of courtyard to what looked like a ruined castle but which he knew must be an old airbenders' temple. Turrets and towers, pillars and pagodas and spiralling staircases, this place had clearly been made by people with a head for heights. Only a few steps took him to the edge. "Blimey, this is high up," he muttered, looking down at the sheer drop, where oddly the clouds were bellow him.

He turned back to the temple, feeling a thrill of excitement, the way he always did when visiting a knew place. It was true, he had been here before, twice in fact but it had looked very different on each occasion and both trips had been short ones. This was a place he didn't know much about and the prospect of meeting the element-benders was truly exciting. They were fascinating.

The Doctor breathed in the tropical muggy air and ran his fingers through his hair. He was eager to meet the Avatar, whoever he was. From what he had seen back at the village it was a man of extraordinary power. Of course The Doctor knew better than anyone that powerful men could also be dangerous ones. He would have to be careful.

The Doctor wandered a little way across the courtyard and could make out two more identical mountain peaks and surrounding them...nothing but clouds and mountain tops. So where were the airbenders?

The Doctor flicked his Sonic Screwdriver and, using the blue light as a torch he entered the temple.

xxx

Aang breathed in and out. He wasn't concentrating on anything in particular but was aware only of the ground beneath him, the sun on his face and the air filling and vacating his lungs. He didn't know how long he had been sitting here but he knew that he felt content and at peace. Slowly, he allowed the thoughts that had been troubling him to float into his mind. With nothing else in the way, he could examine the thoughts and feelings and troubles, accept them and maybe try to come up with a solution. He breathed in and out. Calm...at ease and content...nothing but the air in his lungs -

Something crashed into the side of Aang's head. He gave a yelp as small furry hands fastened themselves around his face and a squawk sounded loud in his ears.

"Momo!" said Aang, sitting up and detaching the lemur from his head. The animal looked at him with huge eyes. "Couldn't you see I was trying to meditate?" but he scratched Momo behind the ears all the same. Momo held up some berries and nuts he had collected, clearly expecting praise. "That's great Momo, well done," he said and the lemur chirruped appreciatively. "Now why don't you go eat them over there."

As Momo scurried off Aang uncrossed his legs and got to his feet. The sun was setting but was still bright, dazzling after having his eyes closed for so long. It shone off the mountains and the tall peaks whose bases were lost in clouds. Aang stretched and yawned widely, then moved nearer the edge of the cliff, where the breeze was stronger. He resumed his position, closed his eyes and breathed.

xxx

Inside the temple, The Doctor felt a sad tug of nostalgia for these people he had never met. The walls were covered in faded paintings and carvings of the airbenders and their bison; their whole history was on these walls. He would have liked nothing more than to wander the halls, looking at the past and piecing together the story of the people that had once lived here. But he carried on, moving carefully in the dark in case he tripped on the strewn rubble and vines. More than once he had to climb over huge rocks and fallen cracked pillars and other bits of debris.

His feet were loud in the echoing chambers but he could also hear the small scurrying of animals and the buzz of insects in the air. Patches of light began to appear where the ceiling had caved in and eventually he could see day light through an archway at the far end of what had once been a vast chamber. He had reached the opposite end of the temple.

As he stepped back into the light and the heat of the sun, The Doctor had to blink a few times as his eyes adjusted. Then he saw, sitting some feet away, a figure. Even from this distance The Doctor could make out the blue airbending tattoos.

The Doctor quietly moved forward. The figure was sitting cross-legged – meditating – on the courtyard floor. The sun was shining of his bald tattooed head and he was wearing bright orange and red robes that fell off one shoulder.

He also seemed to be a child.

The Doctor took another step but before he could say or do anything, the boy turned round and in a flash he was on his feet, taking up a fighting stance. The Doctor could tell that it was purely instinctive; this boy had been drilled into expecting attack. But a second later, the child lowered his arms and stood straighter, a small frown creasing his brow.

"It's you isn't it? You're the stranger everyone was talking about. You stopped the beast back at the village?"

"Uh...yeah, yeah that would be me." Bewildered, the Doctor closed the distance between then, "I'm the Doctor," he said bowing respectfully, as he remembered was the custom here.

The boy looked at him quizzically, weighing him up with grey eyes that were curious rather than accusatory. "I'm Aang," he replied eventually, returning the bow.

"Nice to meet you Aang," he said grinning broadly. "I'm wondering if you can help me. I'm looking for the Avatar. I was told I might find him here."

The boy looked surprised by the question, then he smiled a little bashfully, "You've found him."

The Doctor nodded. He had thought as much. He may not know a lot about this land or about the power held by many of its residence but he knew enough to know that the Avatar was an extremely powerful individual and there was something about this boy...Something more. Something special.

xxx

"The ability to control all the elements," said the man, giving a small half smile and narrowing his eyes as though trying to see inside Aang's mind. "It's incredible."

Aang didn't know what to say to this. The man's appearance wasn't the only think weird about him -though that too was very bizarre; there was the thin strip of materiel around his neck, the shirt and pants that were made from some materiel he had never seem before.

"So...So you didn't know who I was?" said Aang after a while. Since the war, almost everyone he met knew who he was, or at least saw the airbending tattoos and put two and two together.

"Not 'till now, no," said the man who called himself The Doctor, "I've...been away. It's been years since I was last here and..." he looked about him, "things were a lot different back then."

Aang frowned. There was something definitely odd about this man but he seemed friendly enough. "So do you have a name?"

"Just The Doctor," said The Doctor, continuing to look around, and rocking back and forth on his heels. "Where is everyone by the way. What happened to this place?"

Aang raised his eyebrows in incredulity. "You mean you don't know?"

The Doctor gave an apologetic shrug, "Like I said it's been a while." he rubbed his jaw and frowned, "not since the days of Avatar Kyoshi and that was a short trip...run in with a water-serpent, if I remember correctly. Got soaking wet..."

"Wait. Did you just say - "

But the rest of his sentence was drowned out by the low rumble of Appa and a thud as the great bison landed. His friends jumped out of the saddle immediately at the sight of the Doctor, all assuming fighting stances. "Who's the knew guy?" said Toph with distaste. But the Doctor wasn't listening. He was looking at Appa in wonder.

"Oh! You are beautiful!" he said, stepping around to marvel at the great animal.

"This is Appa," said Aang, while surreptitiously giving his friends an _I'll tell you in a minute_ look.

"Just wonderful!" the Doctor beamed, looking delighted but the grin slipped from his face as he turned to find them all staring at him.

"Not to be rude or anything," said Sokka with his arms folded across his chest in a way that suggested that whatever was coming next was going to be anything but polite, "But who are you and why are you dressed like that?"

The Doctor laughed, "I'm the Doctor and I could say the same thing about you."

"This is the man I was telling you about," said Aang quickly, "The one who made one of those creatures disappear."

"Oh, I didn't do that," said the Doctor, putting his hands in his pockets, "Well, it may have recognised the technology of my Sonic Screwdriver and then engaged its teleportation device but...really I didn't do anything."

Aang had no idea what the man was talking about and was about to say so but Toph beat him to it.

"Look," she said stabbing a finger in the Doctor's direction, "Speak plainly or don't speak at all. Did you or didn't you fight one of those dog beasts."

The Doctor looked quite abashed for a moment, then he chuckled, "I'm sorry, what was your name?"

"Toph," she replied shortly, putting her hand on her hips.

"Hallo Toph," said the Doctor beaming again, "Nice to meet you, I'm the Doctor. And yes, I didn't force it to disappear it did that itself. I think when they're in danger they automatically get transported back to their masters."

"Masters?" said Katara, frowning.

"Wait, transported?" interrupted Sokka, "But how? Unless they really are spirit beasts."

"I don't think they're spirit beasts," said the Doctor and Sokka punched the air.

"I knew it!" he shouted, "I told you, it's like they've been made by something. That's why they reacted to the water."

The Doctor looked impressed, "You're quite right."

"Thank you!" said Sokka, looking pleased with himself, "I'm Sokka by the way."

"And I'm Katara," said Katara quickly, "Now I think we all have a lot of talking to do and the sun's almost set. Why don't we set up camp, get dinner going and then we'll talk."

"Great idea! I can help," said the Doctor, looking for all the world as though he was having the time of his life.

As The Doctor followed Sokka and Toph to their camp, Katara caught Aang's arm.

"What do you make of him?" she asked softly.

Aang shrugged, "I really don't know. But he's friendly." Aang grinned, "He might be a little eccentric but I think he's on our side."

xxx

The children spoke little as they set up the camp fire. They set about their jobs with no complaint and with practised ease. He marvelled as he watched Aang light the camp fire with his bending and Katara (whom he now recognised as the girl form the village) waterbending some water into a pot and Toph who, with a flick of her wrist made five blocks of stone rise from the ground for them to sit on. The boy Sokka didn't seem to be a bender but The Doctor noticed the sword in his pack.

The Doctor, at Katara's instruction found some food for Appa and Momo, who he discovered was a flying Lemur. The small creature seemed to have taken a liking to him and had not left the Doctor's shoulder since he had offered it some nuts and berries.

Finally the camp was ready and the stew was bubbling merrily. They each took a place around the fire and a there was a moment's awkwardness. The Doctor could tell that these children were used to being by themselves; an adult's presence was strange to them.

"So...Is it just you then?" said The Doctor conversationally as Katara stirred the stew.

"Yes, it's just us," she said giving him a quick but shrewd look.

"Right. And if you don't my asking – where are your parents? You just seem awfully young to be out here on your own."

Toph laughed loudly and leaned back on her elbows, "I'm sorry" she said, giggling again, "It just always makes me laugh when people think we actually need looking after."  
"Oh, I didn't say that," said the Doctor "It's very clear to me that you do not need looking after. I just wondered what lead four young people to be out in the wilderness alone."

"Well, we're not really alone," said Aang and the Doctor could see the patience in the boy's face. "We have each other and...well...we're..."

"Really powerful," finished Toph with a sly smile.

"Toph," said Katara somewhat sternly. She turned back to The Doctor, "We manage just fine."  
The Doctor smiled at her, understanding. "I can see that. And I don't mean to pry."

Katara smiled at him for the first time since their meeting and then kneeling, she carefully waterbended the stew into rough earthenware bowls, which were passed around the circle.

"Thank you," said The Doctor, feeling oddly at peace. The sun had finally set and a balmy night air was settling in, the buzzing and chirping of insects the only noise.

"So you're a doctor," said Aang after a while, "Are you waterbender?"

"Ah, no no. I'm not," he replied, vaguely remembering from his last visit that some waterbenders had healing powers. "I'm not really that kind of a doctor either. I'm more of a traveller really."

"Oh, well so are we!" said Aang excitedly, "We've been all over the world."

"So what brought you here?" said Sokka and The Doctor got the feeling that they were skirting the questions they really wanted to ask.

"Passing through," said The Doctor, spooning some more stew into his mouth, "This is excellent by the way."

"And where exactly is it you're from?" said Toph without looking at him. The Doctor had already worked out that she was blind but it was easy to forget. The girl must have extraordinary scenes.

"I'm from...far away," he said eventually. He should really have done more research in the Tardis before coming here.

"Well we've been all over the world," the small girl said indignantly, "I bet we'll have heard of it and goodness knows Sokka's looked at enough maps."

"It's fine guys," said Aang softly, "If he doesn't want to say he doesn't have to."

Toph shrugged and went back to her stew.

"But there are some things I'd like to ask you Doctor," said Aang.

"Ask away."

"Do you know what those dog beasts were? They're not like anything I've seen before."

Finished with his stew the Doctor laid the bowl on the ground and pulled one knee towards him. "I don't know exactly what they are but, as Sokka said, they're man-made. Someone created them. I'd say they're either soldiers or scouts or maybe even guard dogs. But someone, somewhere will be controlling them. And you know that's weird because there really shouldn't be any technology like that here. Not yet anyway." He scratched his chin, thinking. It was only a moment before he realised that all four children were staring at him as though he were a mad man.

xxx

"Well, you see the thing is," The Doctor continued, speaking very fast, "I don't think those creatures, those guard dogs or whatever they are, are supposed to be here. I think they're from a different world."

"You mean like the spirit world?" said Katara with a half glance at Aang.

"I don't think so. More like a different planet."

Aang frowned. "How can you know all his?" The man was talking with such certainty but Aang had never heard of anything like this before.

"I've been around a bit," said The Doctor with a sniff.

"But you didn't know what had happened to the airbenders and you didn't know I was the Avatar and..." Aang hesitated, "You mentioned Avatar Kyoshi before. You talked as if you knew her."

"No, no," said the Doctor, waving his hand, "I didn't know her. But I knew some people that knew her."

Aang felt his jaw drop. "But then you'd have to be _really_ old."

"You weren't by any chance trapped inside a giant iceberg, were you?" said Sokka, conversationally.

"No. Though that did nearly happen once at the great glaciers of Galamontoosh. There was this mammoth and..." he suddenly stopped at the look on their faces, "I'm very old." he said.

And suddenly the Doctor looked straight at Aang and for a second they stared at each other. The Doctor didn't look old at all but somehow Aang knew that he was telling the truth. There was something ancient about him, something in the eyes, a history, many histories...lifetimes. Aang was reminded suddenly of the great Lion Turtle. The Doctor blinked and looked away.

"He's telling the truth," said Toph and Aang saw the Doctor's eyebrows go up. "How old are you exactly."

"If I told you you wouldn't believe me."

"Betcha I would. Unless you're lying of course," said Toph with a grin.

"All right then, I'm nine hundred and six."

Sokka burst out laughing, Katara folded her arm in irritation but Toph's eyes widened, "He's telling the truth."

"You are good," said the Doctor, oggling at Toph, "How did you know I was telling the truth."

"Earthbending. I'm really good at it." said Toph simply and The Doctor chuckled.

"I don't understand, how can you be nine hundred and six?" said Sokka, "That's not possible!

"Well, Aang's a hundred and fourteen," said Katara reasonably.

"Are you really?" The Doctor looked at him with shock.

"Yeah, I was the one in the ice berg."

The Doctor nodded in an impressed sort of way.

"Ooh. Ooh! I gottit!" Sokka shouted, sitting up excitedly, "He's a time traveller!"

Katara and Top both rolled their eyes and Aang stoked the fire. The Doctor remained impassive.

"No, no, seriously," continued Sokka, "He said something about knowing someone who knew Avatar Kyoshi, right and his clothes are like nothing from this time and he doesn't know anything abut the war because he _wasn't here_. He time-travelled from the past...or maybe the future."

The Doctor's eyebrows shot up and down and he shook his head. Aang suddenly had the awful thought that maybe Sokka have finally managed to offend him. But then the Doctor grinned, showing all of his teeth, "You are, truly, brilliant. Really, I'm very impressed."

Sokka looked as though he'd been hit over the head with his own boomerang. "Wha..." he looked confusedly at The Doctor.

"I'm a time traveller and I came here from a different planet. I've only visited this world twice before, once in your past – the time of Avatar Kyoshi – and then again in the future. You see, I'm what's called a Time Lord."

The Doctor felt himself ginning; he always loved this bit.

Aang's eyes were wide, Sokka's mouth was hanging open and even Toph was leaning forward, listening hard. Katara however was looking at him shrewdly. "Can you prove it?" she asked, not unreasonably.

"I thought Sokka was cynical one," quipped Toph, "Katara, he's not lying."

"I didn't mean any offence," said the girl quickly, "It's just...i've never heard of anyone being able to travel in time."

"Well, for a long time I didn't know people could bend the elements. And no offence taken."

"So...you're from a different planet?" said Sokka slowly.

"I'm from a planet called Galifrey. My people we...well, I suppose you could say we bend time and space. We... _I_ can travel to any planet at any time."

Sokka was suddenly on his knees looking excited, "So could you take us back in time and stop those things from destroying all the villages? Or even back to the war? You could change everything!"

The boy's face was shining with excitement but he also looked slightly dazed as though he were grappling with concepts too big to tackle – which, The Doctor reminded himself, he was. The Doctor opened his mouth to explain that he couldn't change the past when Aang suddenly spoke up.

"No," he said shortly and for a moment he looked much older than his years. "I don't think it's wise to meddle with time. Everything happens for a reason. We are who we are because of all the things we've lived through. I you change it then...we become someone else or...or we might not even exist!"

The Doctor looked again at the boy, impressed in to silence for a moment. Eventually, he cleared his throat and said, "Aang's right. Certain things in history are supposed to happen, and to change them would have dire consequences."

"But then, aren't you changing history just by being here?" said Katara. "Aren't you changing things right now."

"Not if my being here _is_ the history. Besides everything here is in flux; it can be subject to change."

"I don't think I really understand," said Aang, shaking his head, "But there's to be no changing history." he looked straight at the Doctor with so much authority, he could practically see the past Avatars glaring at him through the years.

"I give you my word," he said, speaking directly to Aang, "That I won't change anything that shouldn't be changed. But those beasts you were fighting – they're not supposed to be here; they're not from this world either and they'll cause a lot of trouble by being here."  
"You don't have to tell us," muttered Toph.

"But I can help you stop them. Find out who's controlling them, find out what they want and see if we can't sort everything out."

Aang smiled, "All right."


End file.
